1. Field of the Invention
The present invention relates to a control system, an image forming system, a control method, and a computer-readable recording medium.
2. Description of the Related Art
Conventionally, in an image forming apparatus that prints an image on a recording medium through an image bearer, components that respectively perform charging, exposure, development, and transfer, is provided around the image bearer, and an image forming unit that performs a series of image forming (also referred to as “printing” or “recording”) processing including image forming is provided. Moreover, in such an image forming apparatus, a light-emitting device array in which plural light emitting devices such as light emitting diodes (LED) are aligned, for example, in a main scanning direction (also referred to as “line direction”) that is perpendicular to a sub-scanning direction is also provided.
In image forming performed by the image forming unit, first, a drum-shaped or a belt-shaped image bearer is uniformly charged by a charging unit. Movement of a drum-shaped image bearer and the like in the sub-scanning direction is also expressed as “rotating” or “turning”. Moreover, movement of a belt-shaped image bearer and the like in the sub-scanning direction is also expressed as “rotating”. Subsequently, the light-emitting device irradiates a charged surface of the image bearer with light in a line unit in the main scanning direction (hereinafter, simply “line”) according to image data, thereby exposing the charged surface. As a result, an electrostatic image (also referred to as “electrostatic latent image”) by light emission is written on the charged surface of the image bearer. Subsequently, by developing the electrostatic image with toner, a toner image is formed on the charged surface. The formed toner image is directly transferred onto a recording medium by a transfer unit, or is transferred onto a recording medium after the image is transferred to a belt-shaped or a drum-shaped intermediate transfer body. The recording medium to which the toner image is thus transferred go through a fixing unit to have the toner image fixed thereon, and is, thereafter, ejected out of the apparatus.
Problems that is concerned about when the light-emitting device array is used in the image forming apparatus are variation in optical output of the multiple light emitting diodes in the light-emitting device array caused at the time of manufacturing the light-emitting device array, and nonuniformity in light amount caused by an assembly error and the like of each light emitting device and an equal-magnification image forming device (rod lens array). The nonuniformity in light amount can cause deterioration of an image, and can appear as vertical streaks in an image printed out. Furthermore, deterioration of an image can include an image skew and the like caused by deviation of a main/sub image position due to an assembly error of the light-emitting device array and the image bearer, or inclination of a main scanning line.
Based on such a background, in the light-emitting device array used in an image forming apparatus, a correction function to make the light amount uniform among the light emitting devices is provided therein in some cases. This correction function is as follows. That is, a correction value to make the light amount uniform is calculated in advance for each of the light emitting devices, and light-amount correction data indicating the correction value is stored in a storage unit such as a read-only memory (ROM). By correcting a driving current to be supplied to each of the light emitting device independently, by using the light-amount correction data of each of the light emitting devices, the light amount is equalized (Japanese Unexamined Patent Application Publication No. 2014-177088).
However, by a method of correcting the driving current of each of the light emitting devices independently as in the above conventional technique, it is necessary to provide a digital-analog converter (DAC) that corrects a driving current based on the light-amount correction data independently for each of the light emitting devices, resulting in an increase in device cost. For example, in an image forming apparatus supporting a resolution of 1200 dots per inch (dpi) and an A3 width (297 mm), approximately 14000 pieces of LED devices are provided. Therefore, if a current correction circuit such as a DAC is provided independently for each of the LED devices, a large scale integrated circuit is required to be designed and mounted therein, leading to a significant increase in device cost.